Multiplying Polynomials 6-2 Multiplying Polynomials Warm Up Lesson Presentation Lesson Quiz Holt Algebra 2

3. h(x) = 4x2 – x + 7.5 find h(0) and h(2) Warm Up Rewrite in standard form. Identify the degree of the polynomial and the number of terms. 1. 9 – x2 + 2x5 – 7x 2x5 – x2 – 7x + 9; 5; 4 2. 23 + 4x3 4x3 + 23; 3; 2 3. h(x) = 4x2 – x + 7.5 find h(0) and h(2) 7.5; 21.5 4. Use your graphing calculator to find the zeros of j(x) = 3x3 – 6x + 6. Round to the hundredths place -1.77

Objectives Multiply polynomials. Use binomial expansion to expand binomial expressions that are raised to positive integer powers.

Example 1: Multiplying a Monomial and a Polynomial Find each product. A. 4y2(y2 + 3) 4y2(y2 + 3) 4y2  y2 + 4y2  3 Distribute. 4y4 + 12y2 Multiply. B. fg(f4 + 2f3g – 3f2g2 + fg3) fg(f4 + 2f3g – 3f2g2 + fg3) fg  f4 + fg  2f3g – fg  3f2g2 + fg  fg3 Distribute. f5g + 2f4g2 – 3f3g3 + f2g4 Multiply.

To multiply any two polynomials, use the Distributive Property and multiply each term in the second polynomial by each term in the first. Keep in mind that if one polynomial has m terms and the other has n terms, then the product has mn terms before it is simplified.

Example 2A: Multiplying Polynomials Find the product. (a – 3)(2 – 5a + a2) Method 1 Multiply horizontally. (a – 3)(a2 – 5a + 2) Write polynomials in standard form. Distribute a and then –3. a(a2) + a(–5a) + a(2) – 3(a2) – 3(–5a) –3(2) a3 – 5a2 + 2a – 3a2 + 15a – 6 Multiply. Add exponents. a3 – 8a2 + 17a – 6 Combine like terms.

Multiply horizontally. Write polynomials in standard form. Check It Out! Example 2a Find the product. (3b – 2c)(3b2 – bc – 2c2) Multiply horizontally. Write polynomials in standard form. (3b – 2c)(3b2 – 2c2 – bc) Distribute 3b and then –2c. 3b(3b2) + 3b(–2c2) + 3b(–bc) – 2c(3b2) – 2c(–2c2) – 2c(–bc) Multiply. Add exponents. 9b3 – 6bc2 – 3b2c – 6b2c + 4c3 + 2bc2 9b3 – 9b2c – 4bc2 + 4c3 Combine like terms.

Example 4: Expanding a Power of a Binomial Find the product. (a + 2b)3 (a + 2b)(a + 2b)(a + 2b) Write in expanded form. (a + 2b)(a2 + 4ab + 4b2) Multiply the last two binomial factors. Distribute a and then 2b. a(a2) + a(4ab) + a(4b2) + 2b(a2) + 2b(4ab) + 2b(4b2) a3 + 4a2b + 4ab2 + 2a2b + 8ab2 + 8b3 Multiply. a3 + 6a2b + 12ab2 + 8b3 Combine like terms.

Multiply the last two binomial factors. Check It Out! Example 4a Find the product. (x + 4)4 (x + 4)(x + 4)(x + 4)(x + 4) Write in expanded form. (x + 4)(x + 4)(x2 + 8x + 16) Multiply the last two binomial factors. (x2 + 8x + 16)(x2 + 8x + 16) Multiply the first two binomial factors. Distribute x2 and then 8x and then 16. x2(x2) + x2(8x) + x2(16) + 8x(x2) + 8x(8x) + 8x(16) + 16(x2) + 16(8x) + 16(16) Multiply. x4 + 8x3 + 16x2 + 8x3 + 64x2 + 128x + 16x2 + 128x + 256 x4 + 16x3 + 96x2 + 256x + 256 Combine like terms.

Notice the coefficients of the variables in the final product of (a + b)3. these coefficients are the numbers from the third row of Pascal's triangle. Each row of Pascal’s triangle gives the coefficients of the corresponding binomial expansion. The pattern in the table can be extended to apply to the expansion of any binomial of the form (a + b)n, where n is a whole number.

This information is formalized by the Binomial Theorem, which you will study further in Chapter 11.

Example 5: Using Pascal’s Triangle to Expand Binomial Expressions Expand each expression. A. (k – 5)3 1 3 3 1 Identify the coefficients for n = 3, or row 3. [1(k)3(–5)0] + [3(k)2(–5)1] + [3(k)1(–5)2] + [1(k)0(–5)3] k3 – 15k2 + 75k – 125 B. (6m – 8)3 1 3 3 1 Identify the coefficients for n = 3, or row 3. [1(6m)3(–8)0] + [3(6m)2(–8)1] + [3(6m)1(–8)2] + [1(6m)0(–8)3] 216m3 – 864m2 + 1152m – 512

Identify the coefficients for n = 3, or row 3. Check It Out! Example 5 Expand each expression. a. (x + 2)3 1 3 3 1 Identify the coefficients for n = 3, or row 3. [1(x)3(2)0] + [3(x)2(2)1] + [3(x)1(2)2] + [1(x)0(2)3] x3 + 6x2 + 12x + 8 b. (x – 4)5 1 5 10 10 5 1 Identify the coefficients for n = 5, or row 5. [1(x)5(–4)0] + [5(x)4(–4)1] + [10(x)3(–4)2] + [10(x)2(–4)3] + [5(x)1(–4)4] + [1(x)0(–4)5] x5 – 20x4 + 160x3 – 640x2 + 1280x – 1024

3. The number of items is modeled by Lesson Quiz Find each product. 1. 5jk(k – 2j) 5jk2 – 10j2k 2. (2a3 – a + 3)(a2 + 3a – 5) 2a5 + 6a4 – 11a3 + 14a – 15 3. The number of items is modeled by 0.3x2 + 0.1x + 2, and the cost per item is modeled by g(x) = –0.1x2 – 0.3x + 5. Write a polynomial c(x) that can be used to model the total cost. –0.03x4 – 0.1x3 + 1.27x2 – 0.1x + 10 4. Find the product. (y – 5)4 y4 – 20y3 + 150y2 – 500y + 625 5. Expand the expression. (3a – b)3 27a3 – 27a2b + 9ab2 – b3